Research On A Fracturing Fluid With High Suspended Sand Ratio And Low Damage

For the characteristics of low permeability reservoirs,the polymer thickener,AT,was synthesized by aqueous monomer copolymerization with acrylamide(AM),2-acrylamido-2-methylpropane sulfonic acid sodium salt(AMPS-Na),alkyl dimethyl allyl ammonium chloride(CnDMAAC)and N,N'-Methylenebisacrylamide(MBA)as monomers,and the optimum polymerization conditions were determined by orthogonal test and single factor experiment:total dosage of monomer is 32%;the ratio of monomers,AM,AMPS-Na,CnDMAAC,MBA,are 93%,1.5%,5.5%and 0.0045%respectively;The dosage of sodium carbonate is 1.2%;The polymerization temperature is 35?;The reaction time is 3 h;The dosage of initiator is 0.024%and the ratio of K2S2O8 and Na2SO3 is 2:1.The performance evaluation of thickener is shown that AT has good solubility,thickening ability and solution stability and can be dissolved within 5 min.The formulation of fracturing fluid,ATF,was determined by using synthetic polymer AT as thickener and selecting other additives by relevant experiments:0.4%ATF base fluid,0.3%T-10,1%KCl,0.1%Na2S2O3,0.05%(NH4)2S2O8.According to the evaluation of rheological property,the fracturing fluid is a kind of pseudoplastic fluid.The flow index,n,is basically unchanged and the consistency index,k,is obviously reduced with the increase of the temperature.The viscosity of ATF can keep above the 57.44 mPa·s after shearing at 90? for 2 h?which shows its excellent shearing and temperature resistance.According to the evaluation of suspended sand performance,either under static condition or shearing condition,the suspension time of ATF is always higher than that of fracturing fluid HF or fracturing fluid VF,which shows its strong ability of suspending sand and recovery after shearing.According to the evaluation of formation damage,the viscosity of broken fluid of ATF can drop below 5 mPa·s and the surface tension is lower than 28 mN/m.The residue content is 57.2 mg/L and the damage rate of artificial core is only 13.71%that is approximate to that of fracturing fluid VF,which shows its low damage to formation.According to the evaluation of filtration loss performance,the filtration loss coeffcient of ATF is 2.84x10-3 m/min1/2,which shows its good performance of filtration loss reduction.According to the evaluation of the frictional resistance,the reduction rate of ATF fracturing fluid reaches 71%when the flow reaches 25 L/min which shows its good frictional resistance.The results can contribute to solve the problem of low suspended sand ratio,flow back difficulty,high residue and high damage to reservoir of conventional fracturing fluid.